Boron nitride nanotube enhanced electrical components

ABSTRACT

Aligned high quality boron nitride nanotubes (BNNTs) can be incorporated into groups and bundles and placed in electronic and electrical components (ECs) to enhance the heat removal and diminish the heat production. High quality BNNTs are excellent conductors of heat at the nano scale. High quality BNNTs are electrically insulating and can reduce dielectric heating. The BNNTs composite well with a broad range of ceramics, metals, polymers, epoxies and thermal greases thereby providing great flexibility in the design of ECs with improved thermal management. Controlling the alignment of the BNNTs both with respect to each other and the surfaces and layers of the ECs provides the preferred embodiments for ECs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit to U.S. Provisional Patent ApplicationNo. 62/092,906, filed Dec. 17, 2014; U.S. Provisional Patent ApplicationNo. 62/153,155, filed Apr. 27, 2015; U.S. Provisional Patent ApplicationNo. 62/180,353 filed Jun. 16, 2015; and U.S. Provisional PatentApplication No. 62/185,329 filed Jun. 26, 2015; and is related toInternational Patent Application No. PCT/US15/27570, filed Apr. 24,2015. The contents of these applications are expressly incorporated byreference.

STATEMENT REGARDING GOVERNMENT SUPPORT

None.

FIELD

The present disclosure generally relates to enhancing the performance ofelectrical components through the inclusion of boron nitride nanotubes.

BACKGROUND

As electronic and electrical components (ECs), such as diodes, lightemitting diodes (LEDs), transistors, integrated circuits and multilayerintegrated circuits, become more prevalent devices, EC performancebecomes more critical. In most instances, EC performance is frequentlylimited by the EC's ability to minimize heat production and improverheat transport away from the heat generating regions to heat sinks,thereby keeping the junction temperatures and component temperatures lowand diminishing thermally-generated mechanical stresses in the materialsand layers making up the EC.

The diodes, transistors, etc. in ECs all have a certain amount ofelectrical resistance. When electrical currents flow in the ECs, heat isgenerated. One parameter of importance is the junction temperature,where one type of semiconductor interfaces with another type ofsemiconductor. This is also the location where much of the resistance islocated. Heat generated at these locations impacts the performanceincluding lifetime of the EC. Removing this heat and keeping thejunction temperatures as low as possible is important for properfunctioning of the EC.

Carbon nanotubes (CNTs), graphene and pyrolytic graphite can beincorporated in ECs where electrically conductive and/or semi conductiveproperties are desired. CNTs and graphene can also favorably affect heattransport and structural strength. However, they do not work where thematerial needs to be electrically insulating. Thus, CNTs have limitedefficacy with respect to enhancing ECs.

Boron nitride nanotubes (BNNTs) have been considered for a number ofprospective applications, such as, for example: enhancing the strengthof ceramic, metal and polymer composites, functionalizing with otherattached molecules for a range of chemical reactions, enhancing thethermal conductivity of certain composites, creating filters andassociated mats, neutron detectors, biomedical interactions includingelectroporation for cancer treatment, piezoelectric devices, andelectrically insulating layers in supercapacitors (also known asultracapacitors).

High quality BNNTs, such as those manufactured by BNNT, LLC of NewportNews, Va., have few defects, no catalyst impurities, 1- to 10-walls withthe peak in the distribution at 2-walls and rapidly decreasing withlarger number of walls. Although dimensions may vary depending on themanufacturing process, BNNT diameters typically range from 1.5 to 6 nmbut may extend beyond this range, and lengths typically range from a fewhundreds of nm to hundreds of microns but may extend beyond this range.

Previous patents and published applications have suggested the additionof materials including BNNTs into the materials going into ECs. See forexample: U.S. Patent Publication US2014/0080954 A1 to Raman et al.; andU.S. Pat. No. 6,864,571 B2 to Arik et al. However, the methods disclosedRaman merely suggest use of BNNTs in bulk, and the methods disclosed byArik merely suggest “generally aligned nanotubes that extend away fromthe catalyst layer” i.e. in the out-of-plane and similar out-of-planeheat transfer for limited aspects of the ECs. Merely dispersing orincluding the BNNTs into the materials going into ECs or out-of-planethermal conductivity is insufficient to enhance the thermal managementin ECs. The chemical vapor deposition (CVD) growth methods of Arik donot produce high quality BNNTs, i.e. few wall, high aspect ratio,minimal defects and catalyst free, as they take place at temperaturesand nitrogen pressures far below what is required for high qualityBNNTs. Indeed, Arik's use of chemical vapor deposition to form BNNTsseverely limits Arik's ability to enhance ECs using BNNT group layers.What is needed are more effective methods for enhancing thermalmanagement in ECs.

BRIEF SUMMARY

This disclosure relates to leveraging the unique properties of BNNTs byincorporating them in electronic and electrical components (ECs for bothelectronic and electrical components). The resultant ECs are enhanced byhaving improved heat management, improved dielectric properties,enhanced ionic transport and enhanced strength. For most of theincorporation of the BNNTs in electronic and electrical components, theimproved or enhanced performance includes having BNNTs that are alignedor partially aligned. This is important as stated in the Backgroundabove because alignment greatly enhances the thermal conductivity andfurther provide desirable dielectric and structural properties. Further,these properties can be directional; for example the alignment cancreate thermal direction “pipes” for transporting the heat in preferreddirections.

The heat conductivity of groups of BNNTs is greatly enhanced when theBNNTs are aligned relative close to each other along their lengths suchthat phonons can couple from one BNNT to another. Also important forenhancing BNNT thermal conductivity is having very long BNNTs with fewwalls and few defects such that phonons have a considerable length topropagate and opportunity to couple phonons to other BNNTs or othermaterials that the BNNTs have been composited with or coated with in thecase of layered composites. Depending on the manufacturing process, highquality BNNTs may have impurities of boron, amorphous BN and h-BN, allof which are also electrical insulating materials.

The pattern of the BNNTs in the materials is important to achieveoptimal performance. In many instances having directionality of the heatflow is desirable and BNNTs as described herein provide thisdirectionality. In other cases uniform heat flow in all directions isdesirable. The optimum configuration is EC-specific, and thus may varyin different embodiments. Further, the electronic properties of the EC,such as the dielectric value, can be enhanced by the appropriatealignment of the BNNTs.

A method for thermal management in an electrical component may includeapplying a BNNT group layer to a contact surface of a material layer inthe electrical component, such that the BNNT group layer is alignedgenerally parallel to the contact surface, such that the BNNTs in theBNNT group layer are generally parallel to the contact surface. In someembodiments, the BNNT group layer may be linearly aligned, such that theBNNTs are also generally parallel to each other. It should beappreciated that “generally parallel” includes embodiments in which thelong axis for the majority of BNNTs in a BNNT group are oriented lessthan 90-degrees relative to the contact surface. In practice, there arevariabilities in the orientation of BNNTs in a BNNT group. For example,a majority of BNNTs may be oriented at less than 90-degrees relative tothe surface, a smaller fraction oriented at less than about 45-degreesrelative to the surface, and an even smaller fraction oriented at lessthan about 15-degrees relative to the surface. Preferably, the long axisfor the majority of the BNNTs are nearly parallel to the contactsurface. In practice, however, BNNTs have non-linear portions, and thusthis specification references “generally parallel” to account fornon-linear portions as well as the variability of BNNTs within a BNNTgroup. The contact surface may include a source and a drain, such as inthe case of a diode. In some embodiments, the EC may be a transistor,and the contact surface may include a source, a gate, and a drain. Insome embodiments the BNNT group layer may out-of-plan to the layers ofthe EC such as to provide a layer-to-layer thermal interconnect. Ofcourse, an EC such as a transistor or a diode may have other materiallayers in contact with a BNNT group layer. The alignment may be linear,such that the BNNTs are generally parallel to each other. Alternatively,the alignment may be two-dimensional or 2-D. The BNNT group layer maybe, for example, a BNNT mat or a BNNT bundle such as BNNT fibers andwoven BNNT yarns. ECs may be fabricated to have one or more of thesefeatures.

A variety of techniques may be used to align the BNNT group layer. Forexample, the layer may be aligned through flattening and/or stretchingprocesses. The BNNTs may also be aligned in the BNNT synthesis ormanufacturing process, as in the formation of BNNT fibers and yarns, oras another example in the formation of a BNNT mat.

In some embodiments, the BNNT group layer may include one or morecompositing materials. The compositing material(s) may be composited inbulk, e.g., generally uniform throughout the BNNT group layer. In someembodiments, the compositing material(s) may be site-specific, e.g.,present at specific portions of the BNNT group layer, such as at certainlocations along the length of a BNNT bundle. Depending on theembodiment, the compositing material may be, for instance, a ceramic, ametal, a polymer, an epoxy, and/or a thermal grease. Some embodimentsmay include a compositing material infused in the BNNT group layer. TheBNNT group layer may be composited with an electrical conductor in someembodiments. In some embodiments the BNNT fibers may be first coatedwith one material and then that coated BNNT fibers are composited with athird material.

The EC may include a BNNT group layer compressed into the materiallayer. Some ECs, such as integrated circuits, may include multiplelayers. In such embodiments, one or more BNNT group layers may besandwiched between material layers in the EC. In some embodiments, aportion of the BNNTs in the BNNT group layer penetrate the contractsurface, such that the BNNT group layer is embedded in the contactsurface. Some embodiments may leave terminal ends of the BNNT grouplayer exposed to the environment, e.g., such that the ends of some ofthe BNNTs may transfer heat directly to the environment (e.g., air oranother medium). In some embodiments, the terminal end may be present ina compositing material, such that the BNNTs transfer heat to thecompositing material.

DRAWINGS

FIG. 1 shows as produced high quality BNNT material and has theappearance of a “cotton ball.”

FIG. 2 illustrates how the randomly aligned BNNT molecules or fibersbecome aligned when flattened or stretched.

FIG. 3 shows a BNNT cotton ball compressed into a mat thereby creatingalignment of the BNNT fibers.

FIG. 4 shows BNNT fibers synthesized in one of the high quality BNNTsynthesis processes where BNNT initial yarns or strands have beencreated.

FIG. 5 shows a BNNT mat made from a filtration process.

FIG. 6 illustrates BNNT yarns/strings woven into a BNNT mat.

FIGS. 7A-7C illustrate BNNT fibers, yarns/strings and weaves compositedwith compositing materials.

FIG. 8 illustrates and end view of in-plane aligned BNNTs between twolayers or sublayers of an EC.

FIG. 9 illustrates a side view of in-plane aligned BNNTs between twolayers or sublayers of an EC.

FIGS. 10A-10C illustrate BNNT bundles with composite interconnects orheat sinks for making connections to layers or sublayers of ECs.

FIG. 11 illustrates a transistor with the aligned BNNTs across thetopside.

FIG. 12 illustrates multiple transistors with aligned BNNTs across theirtopsides.

FIG. 13 illustrates multi-layered transistors with aligned BNNTs acrossthe topsides and, for the lower layer, the bottom side.

FIG. 14 illustrates multi-layered transistors with aligned BNNTs acrosstheir topsides and for the intermediate and lower layers their bottomside with the addition of aligned BNNTs transporting heat across themultiple layers of transistors.

FIG. 15 illustrates a light emitting diode where BNNTs can be utilizedto lower its junction temperature.

DESCRIPTION

The following description is of the best currently contemplated mode ofcarrying out exemplary embodiments of the present approach. Thedescription is not to be taken in a limiting sense, and is made merelyfor the purpose of illustrating the general principles of the presentapproach.

BNNTs may be present in an EC in a group, e.g., several nanotubesforming a layer. The BNNTs in a group may be in various forms, such as,for example, fibers, strands, a mat, or yarn. The alignment of aplurality of BNNTs will impact the heat conductivity of the BNNT group.The heat conductivity of BNNT groups is greatly enhanced when the BNNTsare aligned relative close to each other along their lengths, i.e., thelong axis of each tube generally runs in the same direction.Additionally, BNNT thermal conductivity may be enhanced through usinglong BNNTs, e.g., with lengths more than 1,000 times the nanotubediameter, and preferably more than 10,000 times the diameters, with fewwalls, e.g. 1-10, and preferably with a peak in the 2- and 3-wall range,and few defects, such that phonons may propagate along the long axis ofthe nanotubes. In some embodiments isotopically pure boron may be used,i.e. ¹⁰B or ¹¹B, as the phonon propagation is further enhanced with verypure BNNT material. Very long BNNTs also provide the opportunity forphonons to couple to other BNNTs, or other materials in an EC compositedwith or coated to the BNNTs. Aligned BNNTs can be produced using varioustechniques, including, for example, by certain synthesis processes,stretching and compressing processes, and/or by performing purificationand alignment processes on what may be otherwise unaligned or minimallyaligned BNNTs. These techniques may be used independently or incombination.

High quality BNNTs generally have few defects, no catalyst impurities,1- to 10-walls with the peak in the distribution at 2-walls and rapidlydecreasing with larger number of walls. BNNT, LLC, of Newport News, Va.,produces high quality BNNTs with these parameters, among others. BNNTdiameters typically range from 1.5 to 6 nm but may extend beyond thisrange, and lengths typically range from a few hundreds of nm to hundredsof microns but may extend beyond this range. Depending on themanufacturing process, high quality BNNTs may have impurities of boron,amorphous BN and h-BN, all of which are also electrical insulatingmaterials. In some instances minimizing the amounts of impurities isbeneficial as the amount of BNNT nanotube to nanotube interaction isincreased with less impurities.

Important properties of BNNT include: thermal stability in air to over900 C, thermal stability in most materials to even higher temperatures,strength similar to carbon nanotubes (CNTs), strength maintenance attemperatures over 900 C and temperatures below −269 C. Also, BNNTs arean electrical insulator with approximately a 6 eV band gap, have minimalchemical reactions with most materials, composite well with mostceramics, metals and polymers, and have high thermal conductivity.

Pyrolytic boron nitride can be incorporated in ECs where electricallyinsulating layers are desired. However, they thickness of pyrolyticboron nitride sheets or coatings are typically too thick to provide theclose surface connection to the subcomponents that make up ECs toprovide the desired level of enhanced performance.

Hexagonal boron nitride (h-BN) sheets and flakes similar to graphene canprovide some enhanced thermal management for some ECs due to the thermalconductivity of the h-BN and in some instances the dielectric propertiesof the h-BN. However, the tubular nature of high quality BNNT with theirusually hollow centers provide preferred enhancements in mostembodiments.

The pattern of the BNNTs in the materials in an EC is important toachieve optimal thermal management performance. In many instances havingdirectionality of the heat flow is desirable. BNNTs as described hereinprovide this directionality. In other cases uniform heat flow in alldirections is desirable. Thus, the optimum configuration is EC-specific.Some embodiments may feature multiple configurations. Further, theelectronic properties of the EC, such as the dielectric value, can beenhanced by the appropriate alignment of the BNNTs.

FIG. 1 is a photograph of “as produced” high quality BNNTs available inbulk from BNNT, LLC. The BNNTs in this photograph were produced using ahigh temperature, high pressure synthesis process, and have theappearance of a cotton ball with a tap density of approximately 0.5-1gram/liter. FIG. 2 demonstrates how a combination of stretching andflattening processes may be used to manipulate the alignment of BNNTsshown in FIG. 1. FIG. 2 illustrates randomly aligned BNNT fibers 21, asmay be present in a BNNT ball such as shown in FIG. 1. The alignment ofBNNT fibers 21 illustrated in FIG. 2 progressively increases throughcompression and/or stretching, as illustrated in FIG. 2. It should beappreciated that a variety of mechanical processes may be used toperform compression and/or stretching on BNNTs 21. Flattening processesenhance the 2-D alignment for a BNNT group, while stretching andflattening processes enhance the 1-D or linear alignment of a BNNTgroup.

FIG. 3 shows an example of stretched and compressed BNNT from stretchingand compressing a BNNT ball. A BNNT ball manufactured by BNNT, LLC, wasmechanically compressed between two glass cylinders. The density of thematerial increased by over a factor of 100.

The BNNT manufacturing process also provides alternative methods forproducing aligned BNNTs, and in particular linearly-aligned BNNTs. FIG.4 shows a BNNT initial yarn produced by a synthesis process and the BNNTfibers are partially aligned as part of the synthesis process.International application no. PCT/US15/027570, which is incorporated byreference in its entirety, describes processes for manufacturing BNNTfibers and yarns. These processes are sometimes referred to as dryspinning. In dry spinning processes, the BNNTs naturally align due toVan der Waals forces and pull together for further alignment. BNNTinitial yarns can be infused with compositing material and stretched tofurther enhance the alignment and provide a distribution mechanismuseful in some embodiments.

In some embodiments, BNNT groups such as a BNNT mat may be formedthrough dispersing and filtration processes. BNNTs may be dispersed in afluid dispersant, such as water with a surfactant, alcohol, toluene, andthe like, and then pulled through a filter. A variety of dispersants maybe used, and this disclosure is not intended to be limited to the typeof dispersant. FIG. 5 shows a mat 501 of BNNT produced by dispersing aBNNT ball in ethyl alcohol via sonication, and pulling the alcohol withthe dispersed BNNTs through 40 micron filter paper. The collected BNNTmaterial forms a BNNT mat 501 across the filter that has 2-D alignmentof the BNNT fibers. The BNNT mat 501 is easily peeled off from thefilter. The BNNT mat 501 can be infused with compositing material andfurther stretched. For example, a liquid composite material can bespread over the BNNT mat 501, and then the covered mat can be placed ina vacuum chamber. The vacuum causes the compositing material to fullyinfuse or disperse into the BNNT mat 501. In some embodiments, the BNNTmat 501 can be further compressed and for some compositing materials,heat or light may be applied to the composite so as to harden thecomposite or enhance the bonding into the surface of a material.Lithium-ion batteries include a permeable membrane separator, typicallyformed from a polymeric material, between the anode and cathode. Inembodiments for lithium-ion batteries the BNNT mat 501 may be compressedinto the surface of the polymer separator material. The compression maytake place near the polymer's melting point, thereby infusing thepolymeric material into the BNNT mat, and resulting in a separatormaterial with enhanced strength, thermal conductivity, and porosity. Asone of ordinary skill should appreciate, there are a variety oftechniques for making BNNT mats 501 and combining the BNNT mats 501 withcompositing materials.

FIG. 6 illustrates an example of 1-D or linearly-aligned BNNT yarns 601and 602 woven into a 2-D fabric 600. A variety of weaving technologiesmay be utilized as have been around for millennia. For example, acompositing material may be added to the BNNT strands forming the BNNTyarns 601 and 602 that are being woven into the fabric 600. In someembodiments either chemical or heating processes may subsequently removethe composting material the same way wool is often washed after weaving.Further, similar to the manner in which wool may be died before weaving,some embodiments the BNNT yarns 601 and 602 may be chemically processedand functionalized with the addition of other chemicals prior to orafter the weaving process. The 2-D fabric 600 can have structure, interms of BNNT spacing and density, to match the layout of EC components.For example, certain EC layouts have regularized spacing betweencomponents and the 2-D fabric 600 can be woven to match this spacing.

Additional processes for achieving desired BNNT alignment can involvemaking composites of BNNT and materials such as polymers, and thenstretching the polymer composite in 1-D or 2-D arrangements. Forexample, a bulk composite of BNNT and a heated compositing material canbe extruded via a small orifice to make a composite fiber that as itcools following passing through the orifice turns into a solid materialwith the BNNTs aligned along the axis of the fiber. In anotherembodiment, BNNTs may be dispersed in a liquid or gas flowing through achannel, such that the shear forces improve BNNT alignment in the flowdirection. In some embodiments the BNNTs may be aligned, then thecompositing material is infused with the BNNTs and subsequently, thecomposite may be stretched and/or flattened to further enhance thealignment. It should be appreciated that the degree of alignment mayvary.

It should be appreciated that “generally parallel” includes embodimentsin which the long axis for the majority of BNNTs in a BNNT group areoriented less than 90-degrees relative to the contact surface. Inpractice, there are variabilities in the orientation of BNNTs in a BNNTgroup. For example, a majority of BNNTs may be oriented at less than90-degrees relative to the surface, a smaller fraction oriented at lessthan about 45-degrees relative to the surface, and an even smallerfraction oriented at less than about 15-degrees relative to the surface.Preferably, the long axis for the majority of the BNNTs is nearlyparallel to the contact surface. In practice, however, BNNTs havenon-linear portions, and thus this specification references “generallyparallel” to account for non-linear portions as well as the variabilityof BNNTs within a BNNT group.

FIGS. 7A-7C illustrate sections of BNNT materials infused with acompositing material viewed from above. FIG. 7A illustrates a 2-D BNNTmat 701 infused with a compositing material 703. FIG. 7B illustrates 1-Dor linearly-aligned BNNTs 711 infused with a compositing material 713 toachieve directional heat transport generally in the alignment direction,and structural enhancement. FIG. 7C illustrates a BNNT woven fabric 721infused with a compositing material 723 to provide 2-D direction heattransport, structural enhancements, and dielectric grid. As one ofordinary skill should appreciate from the foregoing, there are a varietyof techniques that can be utilized to achieve alignment of BNNT fibersin a variety of materials.

In general, ECs typically have layers of materials in a variety ofgeometries, including flat sheets and rolls, and often perforated with avariety of interconnections. ECs include one or more layers ofcomponents and in turn each layer may have sublayers of components, suchas semiconductors, dielectrics, electrically insulating or conductivematerials, glues, thermal transport layers, heat sinks, etc. EC layersand sublayers may include materials such as: carbon nanotubes, graphene,Ge, Si, SiO2, Al2O3, InGaN, InGaAs, AlGaN, GaN, SiO, sapphire, otheroxides and semiconductors, aluminum, copper, gold, organics and others.Frequently, one or more layers, or portions thereof, may be doped.Aligned BNNTs may be composited with any of these materials. Dependingon the material, one or more techniques may be used to hold the BNNTs inthe desired position. These include, for example, cooling a melt,hardening polymers including epoxies via heat or light, and mechanicalelements.

BNNTs may be advantageously incorporated in one or more EC layers forthermal management, among other beneficial enhancements. FIG. 8illustrates an end view (or cross-section) of a simple EC layer 80.Layer 80 includes aligned BNNTs 81 between a top layer 82 and a bottomlayer 83. BNNT layer 81 includes impurities 84, which may result fromthe particular manufacturing process used to form the BNNT layer 81.Although not illustrated in FIG. 8, BNNT layer 81 may include acompositing material. The embodiment illustrated in this drawing hasenhanced heat transport out of the page in the in-plane direction, asthat is the direction of the alignment of the BNNTs. In addition, thereis enhanced heat transport out-of-plane as the BNNT fiber-to-fiber, i.e.nanotube-to-nanotube, contact transports heat with enhanced efficiencyin that direction though not to the extent as the heat transport in thedirection of alignment.

FIG. 9 illustrates a side view of the same EC layer 80 illustrated inFIG. 8. When viewed from the side, EC layer 80 includes BNNT layer 91,linearly aligned from left to right, with impurities 94 resulting fromthe manufacturing process. The degree of alignment illustrated in thisdrawing is somewhat low, as there are some BNNTs nearly vertical. Itshould be appreciated that the degree of alignment may vary depending onthe manufacturing and processing used in a particular embodiment.Generally, however, the BNNTs in a group are preferably aligned suchthat the long axis of each nanotube is oriented in the same generaldirection. Because BNNTs produced by most manufacturing processes arenot perfectly linear structures, but instead as shown in FIG. 4 includevarious twists, bends, and non-linear lengths, it should be understoodthat FIG. 9 approximates each BNNT as a cylinder, and shows the generalorientation of each cylinder as sloping in a direction generallyparallel with the contact surface of layers 92 and 93. The BNNT layer 91is positioned between the top layer 92 and bottom layer 93. In thisembodiment, the BNNT layer 91 is slightly embedded in the two adjacentlayers 92 and 93, such that a portion of some BNNTs penetrates a layer.In this example, embedding is not uniform, as may be the situationdepending on the materials used for layers 92 and 93. Although notillustrated in FIG. 9, a compositing material such as ceramics, metalsand polymers may be included with the BNNT layer 91. It should beappreciated that a compositing material may be included in eachembodiment, even though not illustrated in a drawing or explicitlyreferenced in this description.

In some embodiments, a BNNT group layer may feature one or moresite-specific infused compositing materials. A site-specific infusionrefers to an infusion present at only a portion of the BNNT group layer,such as infusions at separate locations along a length of a BNNT bundle.FIGS. 10A-10C illustrate examples of aligned BNNTs with site-specificinfused compositing materials. FIG. 10A illustrates linearly-alignedBNNTs 101 with a few impurities 104. The arrows show the direction ofheat transfer. FIG. 10B illustrates the aligned BNNTs 101 infused withseparate compositing materials 102 and 103 at separate locations.Compositing materials 102 and 103 may be useful for interconnecting thealigned BNNTs to other components or layers in an EC. For example,solders, droplets of compositing material, etc. may be injected ordeposited at appropriate locations in the EC. FIG. 10C illustrates threedifferent compositing materials 105, 106, and 107 infused with thealigned BNNTs 101 at separate locations. As one of ordinary skill willappreciate, great flexibility is achievable in terms of the geometriesand materials utilized. Compositing materials may be electricallyinsulating, electrically conducting, or semiconductor materials,depending on the need for the compositing material at the particularsite. Due their stability at high temperature, the BNNTs will work withdissimilar materials, e.g. one portion of an EC can be a ceramic andanother portion may be a metal, a different ceramic, a polymer, a metal,or a repeat of any of the former.

Processes for fabricating ECs having BNNT layers include: laser drivensintering of ceramics, laser driven melting of metals, and forming theBNNT layout of felts, yarns and/or fabrics with polymers, then oxidizingaway the polymer and dispersing the ceramic(s) and/or metal(s) into theBNNTs, and then heating to lock in the dispersed ceramics(s) and/ormetal(s). As one of ordinary skill in the fabrication will appreciate,there is an extremely diverse set of technologies that are utilized tofabricate EC and the methods vary layer by layer and sublayer bysublayer as the materials properties of the specific layer or sublayer.The technique for incorporation of the BNNTs into the specific layer orsublayer must be specific to the particular material forming the layeror sublayer.

Heat transport in ECs may be enhanced by BNNT bundles, yarns and/orstrings, transporting heat between the layers and in multilayerstructures. The term BNNT “bundle” refers to a plurality of BNNT groups,strings, or yarns, forming a single mass of BNNTs. In some instances,the heat transfer may be enhanced by the presence of compositingmaterial in contact with the BNNTs and, in some embodiments, the EClayer or sublayer. For example, the BNNTs may be composited withceramics, metals, polymers, epoxy, thermal grease, or other materialinfused by CVD, plasma, electron beam, ion beam processes, etc. ingeometries such that the BNNTs have thermal connection to the EC layers.The material used for the connection to one layer may be different fromthe material used for connection to other layers of the EC. The BNNTs,or a portion thereof, may be electrically insulated from one or morelayers to take advantage of their dielectric or non-electricalconductivity properties. BNNTs may be composited with an electricalconductor to provide both heat transport and electrical conductivity.Small particles of amorphous BN, h-BN, and boron may also be present andin most embodiments the performance is enhanced if the amount of thesesmall particles is minimized.

Heat predominantly propagates along the long axis of aligned BNNTs 101illustrated in FIG. 10A and is released to the environment near the endsof the bundle of aligned BNNTs 101. The exterior ends of the sublayerbundle of BNNTs 101 illustrated in FIG. 10A are open to the surroundingenvironment that would typically be air, but could be other mediums ormaterials. The exterior ends of the sublayer bundle of BNNTs 101 in FIG.10B are embedded in compositing materials 102 and 103, which may be heatsinks comprised of, for example, aluminum, gold, pyrolytic graphite,and/or thermally conductive epoxy, etc. The exterior ends of the bundleof BNNTs 101 in FIG. 10C are embedded in compositing materials 105 and107, that could be, for example, heat sinks or connectors comprised ofaluminum, copper, gold, pyrolytic graphite, and/or thermally conductiveepoxy, etc. It should be appreciated that the compositing materials 105and 107 may be formed of similar or dissimilar materials, depending onthe embodiment. Further, there may be an intermediate compositingmaterial 106 that could be another heat sink or connector, comprised of,for example, any one of the aforementioned materials. As one of ordinaryskill should appreciate, this sequence of heat sinks of similar ordissimilar materials may be repeated along the bundle of BNNTs 101 anynumber of times.

As an example embodiment, FIG. 11 illustrates a transistor 1100 with asource 112, gate 113 and drain 114. These three subcomponents may beplaced on or be embedded within a number of sublayers of insulating,semiconductive, and conductive materials 115-118 and there may be a heatsink subcomponent 119. The configuration illustrated in FIG. 11 ismerely demonstrative, and additional or fewer sublayers may be presentdepending on the particular device. The gate 113 may be eliminated tocreate a diode. In the case of an LED, a layer of transparent materialmay cover the source 112 and drain 114. Note, BNNTs are opticallytransparent to IR and visible light, and thus would not impede an LED.Many of the subcomponents, including the source 112, gate 113, drain114, and sublayers 115-118, may typically be only a few nm to a few tensof nm in thickness, but may extend beyond these ranges depending on theparticular EC. Thickness of sublayers close to the source, gate anddrain are typically a few nm to a few tens of nm, but may extend beyondthis range including up to mm or more, for PCB, PWB and heat sinksublayers (if present). Additional sublayers may be present compared towhat is illustrated in FIG. 11. The source 112, gate 113, and drain 114may or may not have simple shapes and may or may not be embedded in thetop sublayer(s). The spacing 1110-1114 between the source 112, gate 113and drain 114, are typically in the range of 0.1 to 5 microns, but insome embodiments may extend beyond this range or be below this range,especially for multilayer ECs, including, for example, integratedcircuits (ICs). Some ECs may have other subcomponents, such asresistors, capacitors, etc.

The BNNTs 111 illustrated in FIG. 11 are illustrated as a top-sidesublayer but could be on other surfaces such as the bottom-side. Havingmostly small diameters of only 1.5-6 nm, the BNNTs 111 can closelycontact or interface with the source 112, gate 113, drain 114, andnearby materials, and transport heat away from the critical areas wherethe source 112, gate 113, and drain 114 make a junction with thesublayer(s) they are in contact with, thereby lowering the junctiontemperature(s) for a given level of current flowing through the device.The BNNTs 111 are also in close contact with each other, therebyproviding the paths for phonons to flow from one BNNT to other BNNTs.The phonon flow may also occur via a coating, compositing or connectingmaterial such as an epoxy, thermal grease, local gas, etc. FIG. 11 is across section view in the plane perpendicular to the direction of thealigned BNNTs 111 so the heat is being transported out of the plane ofthe figure. In addition to the BNNTs 111 illustrated are boron,amorphous BN or h-BN particles 1115. To enhance performance, theseparticles are minimized both for the number of particles and their size.

The aggregate width 1117 of the sublayer bundle of BNNTs 111 may varyfrom some 10s of nm to 100s of microns or even 10s of mm depending onthe device. The width 1117 is dependent on the widths and spacing of thesource, gate (if present), drain, resistors, capacitors, etc., and thewidth 1117 is dependent on the amount of heat generation from the ECexpected to be transported. The height or thickness 1116 of the sublayerbundle of BNNTs 111 is dependent on the feature size of thesubcomponents, the amount of compositing or coating material (ifpresent), the distance to other adjacent layers and sublayers, and theamount of heat to be transported.

FIG. 12 illustrates an EC 1200 having three transistors 121, 122 and 123fabricated on the same layers. Clearly any number can be put on a givenlayer, e.g. 2, 3, 4, . . . , millions or even billions in the case ofsome ICs. In addition, the subcomponents illustrated as transistorscould instead be diodes, LEDs, resistors, capacitors, etc., depending onthe EC. In all cases the BNNTs 111 as illustrated in FIG. 11 along withany coatings or compositing materials, may be placed across the multiplesubcomponents to enhance transport of heat in the direction into or outof the page.

FIG. 13 illustrates an EC 1300 with two layers 131 and 132 similar tothe layer illustrated in FIG. 12, forming a multilayer IC. A single heatsink 133 is included in this embodiment. The layer of BNNTs 1301 forms aback-side layer to the upper layer 132, while being a top-side layer forthe lower layer 131. Interlayer connects and subcomponents such ascapacitors are not illustrated, but as one of ordinary skill in the artshould appreciate, a number of interconnects, sublayers, andsubcomponents may make up the multilayer IC 1300. The bundles BNNTs 111illustrated in detail in FIG. 11 and BNNT layers illustrated in FIGS. 12and 13 are providing enhanced heat transport for the EC, as well asmaterial structural enhancements, and thereby improving performances ofthe ECs. In addition, the BNNTs bundles provide modified dielectricconstants, in particular lower dielectric constants due to the porosityof the BNNTs, which for ECs and ICs operating with varying electricalflows will reduce the component heating in most applications.

FIG. 14 illustrates an embodiment of an EC 1400 with three primarylayers 148, 149 and 1410 EC. Each primary layer in this embodimentincludes multiple sublayers 142-146 for illustrative purposes, andmultiple components 147. A single heat sink 141 is illustrated, thoughin practice there may be other heat sinks, such as top-side heat sinks.The BNNT layers 146 provide thermal conductivity and low dielectricproperties in a direction into and out of the drawing. The dielectricproperties may be manipulated by controlling the level of alignment ofthe BNNTs going into the BNNT layers.

Inter-layer and sublayer BNNT interconnects 1412 and layer and sublayerconnections 1411, 1413, and 1414, provide thermal transport that can beeither electrically insulating with associated dielectric properties, orelectrically conductive or semiconductive. In some embodiments,different sublayers may have different properties, e.g., one sublayermay be electrically insulating and another sublayer may be electricallyconductive. The BNNT interconnect 1412 and sublayer connections 1411,1413, and 1414, may be, for example, a BNNT bundle cut to precisely fitthe application. For example, the BNNT bundles can be prepared as astring or yarn with the various compositing materials interspersedperiodically along the BNNT bundle for interconnecting to theinter-layer connection points, and the BNNT string or yarn can bethreaded through the interconnect locations. The selection of ceramic,metal, and/or polymer material utilized to composite or coat the BNNTsand/or portions thereof, may be used to control the properties ofsublayers. For example, portions of the BNNTs in a first sublayer may becomposited or coated with a ceramic, and portions of the BNNTs in asecond sublayer may be composited or coated with a polymer material. Inthis way the thermal connection to a given layer can be enhanced byoptimizing the compositing or coating material for the thermalconnection to the materials in the given sublayer or layer.

Interlayer connects and subcomponents such as metal conductors,capacitors and interconnects for connecting the EC to other componentsare not illustrated, but as one of ordinary skill in the art of ICs andmultilayer ICs should appreciate, a very diverse number ofinterconnects, sublayers and subcomponents may make up a multilayer IC.

Diodes, including light-emitting diodes, represent another category ofECs that may benefit through the incorporation of BNNTs. FIG. 15illustrates a light emitting diode 1500 that includes the followinglayers and components: heat sink 151, baseplate 152, interface 153,solder 154, transition heat sink 155, attach layer 156, emitter or LEDemitter 157, phosphor 158, resin-glue 159, lens 1510 and/or electrode1511. These layers and components are meant to be illustrative of commonlight-emitting diodes, and embodiments may vary. In select embodiments,BNNTs can be included in any layer that can be made of compositingmaterials compatible with being composited with BNNTs to include theheat sink 151, solder 154 resin-glue 159 and lens 1510. For example,including BNNTs in resin-glue layer 159 allows for lowering the criticaljunction temperature of the emitter or LED emitter 157. Further, theBNNT increases the porosity and thereby lowers the dielectric value ofthe resin-glue layer 159, providing lower heat going into the attachlayer 156 junction.

Generally, the geometry of the BNNTs used for multilayer interconnectsmay vary greatly in cross sectional area and length. The BNNTsthemselves are typically in the 1.5 to 6 nm diameter and their lengthscan vary from 10s of nm to 100s of microns. Consequently a great rangeof possibilities for assembling small to very large numbers of BNNTs toform the BNNT bundles, yearn and/or strings.

FIGS. 8, 9, 10, 11, 12, 13, and 14 show the BNNT bundles to be in-planeor mostly in-plane. FIG. 14 shows some BNNT bundles that areout-of-plane with reference to the three layers illustrated and theirsublayers. In all instances, the preferred heat transport is in thedirection of the aligned BNNTs. However, the close contact of the BNNTscreates BNNT tube-to-tube or fiber-to-fiber contacts that also enhancethe heat conductivity across the BNNT fibers. So while the primary heatpath is along the length of the BNNTs, there is also enhanced heatremoval across the BNNT fibers. The result is that careful management ofthe BNNT alignment enhances the heat management in the ECs far beyondjust putting BNNTs into the bulk materials as proposed by Raman or justputting BNNTs out-of-plane in limited locations as proposed by Arik.

BNNTs provide the designer and fabricator of ECs great flexibility inengineering effective heat transport and electrical properties into ECs.The BNNT layer transports heat from the hottest regions to coolerregions where the heat can be dissipated from the EC.

Heat transport in ECs may be enhanced by BNNT tube contact with thetop-side and bottom-side materials in addition to being composited intomaterials making up the layers and multilayer structures. In someinstances the heat contact may be enhanced by the presence ofcompositing material in contact with the BNNTs and the EC subcomponents.For example, the BNNTs may be uncoated or coated with thin amounts ofepoxy, thermal grease, or other material infused by CVD, plasma,electron beam, ion beam processes, etc. Small particles of amorphous BN,h-BN, and boron may also be present. Clamps or glues may be used toassist in keeping the BNNTs in contact with the top-side, bottom-side,etc. components.

As one of ordinary skill should appreciate, the embodiment describedherein range from nanometers to centimeters in a single figure, i.e.seven orders of magnitude in scale. Many of the beneficial effectsgenerally occur due to the few nm diameter of the typical BNNT coming inclose contact with the few nm to micron scale structures of the ECs andtransporting the heat to heat sinks, plus the ability of high qualityBNNTs to transport heat from BNNT to BNNT thereby greatly spreading andtransporting the heat over much longer distances and much larger areas.BNNTs provide the designer and fabricator of ECs and ICs greatflexibility in engineering effective heat transport into ECs. The BNNTtransport heat from the hottest regions to cooler regions where the heatcan be dissipated. The BNNTs being electrical insulators provide minimalinterference with the electrically conductive materials in the ECs whileoffering the designer a new tool for the introduction of porosity at thenm and micron scales the optimize the dielectric properties such asachieving low-k for lower electrical loss and consequently lowerheating, while at the same time the BNNTs' strength provides structuralenhancements valuable for high temperature operation and thermal cyclingof the ECs.

In all the above processes there may be some amounts of particles ofamorphous boron, amorphous boron nitride (BN) and/or hexagonal-boronnitride (h-BN) (sometimes referred to as BN platelets). Depending on thechemical character of the layer a purification step may be utilized toremove these particles to achieve enhanced thermal conductivityperformance. In some cases these particles may contribute to theenhanced thermal conductivity. The ECs will also be more resilient toexternal forces by the addition of BNNT due to its exceptional strength.The BNNT based composites will better withstand large thermalvariations, vibrations, accelerations, etc. thereby providing improvedperformance especially in extreme environments.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the approach. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The principles described herein may be embodied in other specific formswithout departing from the spirit or essential characteristics thereof.The present embodiments are therefore to be considered in all respectsas illustrative and not restrictive.

What is claimed is:
 1. A method for thermal management in an electricalcomponent, the method comprising: applying a BNNT group layer to acontact surface of a material layer in the electrical component, whereinthe BNNT group layer is aligned generally parallel to the contactsurface such that the BNNTs in the BNNT group layer are alignedgenerally parallel to the contact surface, and wherein at least aportion of the BNNTs in the BNNT group layer penetrate the contactsurface, such that the BNNT group layer is embedded in the contactsurface.
 2. The method of claim 1, wherein the BNNT group layer iscomposited into the material layer.
 3. The method of claim 1, whereinthe BNNT group layer is linearly aligned, such that the BNNTs in theBNNT group layer are aligned generally parallel to each other.
 4. Themethod of claim 1, wherein the BNNT group layer comprises a BNNT mat. 5.The method of claim 1, wherein the BNNT group layer comprises a BNNTbundle.
 6. The method of claim 1, further comprising flattening the BNNTgroup layer.
 7. The method of claim 1, further comprising stretching theBNNT group layer in a first direction, and wherein the BNNT group layeris applied to the contact surface such that the first direction isgenerally parallel to the contact surface.
 8. The method of claim 1,further comprising forming the BNNT group layer by: dispersing BNNTs ina dispersant, and pulling the dispersed BNNTs and dispersant through afilter.
 9. The method of claim 1, wherein the BNNT group layer comprisesat least one compositing material.
 10. The method of claim 9, whereinthe at least one compositing material is at least one of a ceramic, ametal, a polymer, an epoxy, and a thermal grease.
 11. The method ofclaim 9, wherein the BNNT group layer is infused with the at least onecompositing material.
 12. The method of claim 1, wherein the BNNT grouplayer is composited with an electrical conductor.
 13. The method ofclaim 1, further comprising compressing the BNNT group layer into thematerial layer.
 14. The method of claim 1, wherein the BNNT group layercomprises woven BNNT yarns.
 15. The method of claim 1, wherein a firstside of the BNNT group layer contacts the contact surface of thematerial layer, and further comprising positioning a second materiallayer on a second surface of the BNNT group layer.
 16. The method ofclaim 1, further comprising forming a site-specific infusion on the BNNTgroup layer, such that a compositing material is infused in a portion ofthe BNNT group layer.
 17. The method of claim 1, wherein the BNNT grouplayer comprises a terminal end, and the terminal end is exposed to theenvironment.
 18. The method of claim 1, wherein the BNNT group layercomprises a terminal end, and further comprising embedding the terminalend in a compositing material.
 19. The method of claim 1, wherein thecontact surface includes a source and a drain.
 20. The method of claim19, wherein the BNNT group layer is in contact with the source and thedrain.
 21. The method of claim 1, wherein the contact surface includes asource, a gate, and a drain.
 22. The method of claim 21, wherein theBNNT group layer is in contact with the source, the gate, and the drain.23. The method of claim 22, wherein the BNNT group layer is compositedinto the material layer.
 24. An electrical component comprising: amaterial layer having a contact surface, and a BNNT group layer incontact with the contact surface; wherein the BNNT group layer comprisesBNNTs aligned generally parallel to the contact surface, such that theBNNTs in the BNNT group layer are aligned generally parallel to thecontact surface, and wherein at least a portion of the BNNTs in the BNNTgroup layer penetrate the contact surface, such that the BNNT grouplayer is embedded in the contact surface.
 25. The electrical componentof claim 24, wherein the BNNTs forming the BNNT group layer aregenerally parallel to each other.
 26. The electrical component of claim24, wherein the contact surface includes a source and a drain.
 27. Theelectrical component of claim 26, wherein the BNNT group layer is incontact with the source and the drain.
 28. The electrical component ofclaim 24, wherein the contact surface includes a source, a gate, and adrain.
 29. The electrical component of claim 28, wherein the BNNT grouplayer is in contact with the source, the gate, and the drain.
 30. Theelectrical component of claim 24, wherein the BNNT group layer comprisesat least one of a BNNT mat and a BNNT bundle.
 31. The electricalcomponent of claim 24, wherein the BNNT group layer comprises at leastone compositing material.
 32. The electrical component of claim 31,wherein the at least one compositing material is at least one of aceramic, a metal, a polymer, an epoxy, and a thermal grease.
 33. Theelectrical component of claim 31, wherein the BNNT group layer isinfused with the at least one compositing material.
 34. The electricalcomponent of claim 24, wherein the BNNT group layer is composited withan electrical conductor.
 35. The electrical component of claim 24,wherein the BNNT group layer is compressed into the material layer. 36.The electrical component of claim 24, wherein a first side of the BNNTgroup layer is in contact with the contact surface of the materiallayer, and further comprising a second material layer on a secondsurface of the BNNT group layer.
 37. The electrical component of claim24, wherein the BNNT group layer comprises a site-specific infusion,such that a compositing material is infused in a portion of the BNNTgroup layer.
 38. The electrical component of claim 24, wherein the BNNTgroup layer comprises a terminal end, and the terminal end is exposed tothe environment.
 39. The electrical component of claim 24, wherein theBNNT group layer comprises a terminal end, and further comprisingembedding the terminal end in a compositing material.